MOIRCS Spectroscopy Mode: Information

How To Make an OPE File for Spectroscopy Observation

Please read the following documents before your observation.

Manual and sample OPE files (for spetroscopic observation)

Description of an OPE file: Guide to MOS Observation with MOIRCS [Under Construction]
Sample OPE file for spectroscopy observation: template_spec_030910.ope (Caution!! UNIX or Linux only-- Last update: 2010-03-09))

Flat Fielding/Comparison

We usually use the bare aluminum backsurface of the top screen which is illuminated by domelamp as the spectroscopic dome-flat source. Dome flat data will be taken before and after the observation. Usually we do not take the dome data with the dome light off. Instead the dark data under the same exposure may be used for subtraction. If you need the additional data, like the lamp-off data too, please explicitly request it before the observation.

There is also the other light source for flatfielding of spectroscopic data. The halogen lamp on the calibration probe may work as a light source, though it only illuminate a part of the field of view. We take the flat data at least on 5 cal-probe position in order to illuminate the whole MOS area.

Th-Ar comparison lamp is available for the wavelength calibration. We take the comparison data by scanning the entire MOS field of view (5 exposure is at least necessary). Usually, in NIR window there are much OH night sky lines so we do not need to take comparison. But there are some wavelength region where the OH line is relatively poor (e.g. red side of K window). The nightlines may be blended on the low-dispersion grism data under wider slit width. We can take comparison on request.

Autoguider Issue

As the MOIRCS FOV occupies much of the Cassegrain focal area, the position we can choose an AutoGuider (AG) star without vignetting is rather limited. A star with visual magnitude of 9 to 15 magnitudes (R-band: 650 nm) are necessary for Autoguider. Such a bright stars are relatively sparse in high Galactic latitude, and occasionally it is difficult to find such star in the non-vignetting area. In this case we may ask putting the AG probe to the area which will cause vignetting. If you are unlucky, you may lose your most important target by the AG shadow. To avoid such unfortunate case, all MOS or NB imaging observers shoud check the availability of the AG stars before the observation to avoid the possible loss of important targets.

The diameter of the shadow by the Autoguider has 72 arcseconds. We can choose any bright stars within 4'.6-radius area from the FOV center in the Cassegrain focal area (See figure below). But if you want to avoid vignetting by the shadow of the AG probe, the area we can choose is limited to at least 72" away from any of your slitlets. The blue-colored area in the bottom figure indcates the "safe" region, where the shadow of the AG probe will never cause vignetting on the area you may put slitlets. If you can find a star that is more than 72" away (but within 4.6' from the center of the FOV) from the longward edge of the preimage, it is best for the AG star.

Another issue is the affection of the Moon, cloud, or twilight onto the AG. As is written in the Imaging Information page, the AG may not work properly if the Moon is close to your target less than 20 degrees. If cirrus/clouds come into the field of view during the observation, the autoguider may quickly lose the star, which will lead the loss of the MOS alignment. As the MOS acquisition takes long time, it is not recommended to push the spectroscopic observation under cloudy condition. The twilight in morning time will also change the background level very quickly and the AG will become unavailable. Usually we ask to take preimaging data during the morning time.

Bad Data During Oct 30th to Nov 2nd 2007

Some data taken during Oct 30th to Nov 2nd may have suffered from the affection of trouble in channel-1 filter turret. Please do not use the channel-1 data during the period.

Stray Light on Spectroscopy Data

Before September 2006 the spectroscopic data affected by a significant amount of stray light. That is mechanically fixed and now the effect is minor, though under the observation of zJ500 grism without the order-sorting filter it still remains slightly.

All the information about the fixing work in 2006 can be found here.

Spectroscopic Data Reduction Software

Not available yet, and unfortunately, no action is going on. Some people/groups outside observatory are trying to make it. They may open to public in the future.

If you are developing your own software and want to put the link to your software website here, please contact to Ichi Tanaka (ichi ### subaru.naoj.org: change ### to @). We will greatly appreciate your contribution.

Please note that all data on these pages are subject to change as the evaluation of the performance of MOIRCS progresses.
For more details, please make contact to the SS.

Updated 2009-08-19